Evaluating the Durability of Lime-Stabilized Soil Mixtures using Soil Mineralogy and Computational Geochemistry
| Autor: | Dallas N. Little, Saureen Rajesh Naik, Pavan Akula |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Mechanical Engineering
0211 other engineering and technologies 02 engineering and technology engineering.material 010502 geochemistry & geophysics 01 natural sciences Durability Soil mineralogy 021105 building & construction engineering Environmental science Geotechnical engineering Clay soil 0105 earth and related environmental sciences Civil and Structural Engineering Lime |
| Zdroj: | Transportation Research Record: Journal of the Transportation Research Board. 2675:1469-1481 |
| ISSN: | 2169-4052 0361-1981 |
| Popis: | Lime stabilization is a common technique used to improve the engineering properties of clayey soils. The process of lime stabilization can be split into two parts. First, the mobilization and crowding of [Formula: see text] ions or [Formula: see text]molecules from hydrated lime at net negative surface charge sites on expansive clay colloids. Second, the formation of pozzolanic products including calcium-silicate-hydrate (C-S-H) because of reactions within lime-soil mixtures. The pozzolanic reaction is generally considered to be more durable, while the [Formula: see text] adsorption has been associated with more easily reversible consistency changes. This study offers a protocol to assess whether the stabilization process is dominated by durable C-S-H (pozzolanic) reactions or a combination of cation exchange and pozzolanic reactions. Expansive clays with plasticity indices >45% from a major highway project in Texas are the focus of lime treatment in this study. The protocol consists of subjecting lime-soil mixtures to a reasonable curing period followed by a rigorous but realistic durability test and investigating the quality and quantity of the pozzolanic reaction product. Mineralogical analyses using quantitative X-ray diffraction (XRD) and thermogravimetric analysis (TGA) indicates the formation of different forms of C-S-H. In addition, geochemical modeling is used to simulate the lime-soil reactions and evaluate the effect of pH on the stability of C-S-H. The results indicate C-S-H with Ca/Si ratio of 0.66 as most the stable form of C-S-H among other forms with Ca/Si ratio ranging from 0.66 to 2.25. The effect of reducing equilibrium pH on C-S-H is also evaluated. A reduction in pH favored dissolution of all forms of C-S-H indicating the need to maintain a pH ≥ 10. |
| Databáze: | OpenAIRE |
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